Optimization of on-line hydrogen stable isotope ratio measurements of halogen- and sulfur-bearing organic compounds using elemental analyzer-chromium/high-temperature conversion isotope ratio mass spectrometry (EA-Cr/HTC-IRMS).

Rationale: Accurate hydrogen isotopic analysis of halogen- and sulfur-bearing organics has not been possible with traditional high-temperature conversion (HTC) because the formation of hydrogen-bearing reaction products other than molecular hydrogen (H ) is responsible for non-quantitative H yields and possible hydrogen isotopic fractionation. Our previously introduced, new chromium-based EA-Cr/HTC-IRMS (Elemental Analyzer-Chromium/High-Temperature Conversion Isotope Ratio Mass Spectrometry) technique focused primarily on nitrogen-bearing compounds. Several technical and analytical issues concerning halogen- and sulfur-bearing samples, however, remained unresolved and required further refinement of the reactor systems.

Carbon, Hydrogen and Chlorine Stable Isotope Fingerprinting for Forensic Investigations of Hexachlorocyclohexanes.

Multielemental stable isotope analysis of persistent organic pollutants (POPs) has the potential to characterize sources, sinks, and degradation processes in the environment. To verify the applicability of this approach for source identification of hexachlorocyclohexane (HCHs), we provide a data set of carbon, hydrogen, and chlorine stable isotope ratios (δC, δH, δCl) of its main stereoisomers (α-, β-, δ- and γ-HCHs) from a sample collection based on worldwide manufacturing. This sample collection comprises production stocks, agricultural and pharmaceutical products, chemical waste dumps, and analytical-grade material, covering the production time period from the late 1960s until now.

Improvement of analytical method for chlorine dual-inlet isotope ratio mass spectrometry of organochlorines.

Rationale: The development of compound-specific chlorine isotope analysis (Cl-CSIA) is hindered by the lack of international organochlorine reference materials with isotopic compositions expressed in the δ(37) Cl notation. Thus, a reliable off-line analytical method is needed, allowing direct comparison of the δ(37) Cl values of molecularly different organic compounds with that of ocean-water chloride, to refer measurement results to a Standard Mean Ocean Chloride (SMOC) scale.

Methods: The analytical method included sealed-tube combustion of organochlorines, precipitation and subsequent conversion of formed inorganic chlorides into methyl chloride (CH3 Cl) for the determination of δ(37) Cl values by Dual-Inlet Isotope Ratio Mass Spectrometry (DI-IRMS).

Validation of user- and environmentally friendly extraction and clean-up methods for compound-specific stable carbon isotope analysis of organochlorine pesticides and their metabolites in soils.

In order to evaluate the potential of compound-specific stable carbon isotope analysis (CSIA) for tracking organochlorine pesticides in soil systems, sample pre-treatment methods have to be developed, which can provide recoveries sufficient for low detection limits without altering the isotope ratio of the target compounds. In this study we tested the compatibility of CSIA with user- and environmentally friendly extraction methods, including the Quick, Easy, Cheap, Effective, Rugged and Safe procedure (QuEChERS), Ultrasonic Assisted Extraction (USE) and Focused Ultrasonic Extraction (FUSE), as well as clean-up methods, including sulfuric acid clean-up and Florisil(®) column chromatography for hexachlorocyclohexanes (HCHs), p,p'-dichlorodiphenyltrichloroethane (DDT) and their environmental metabolites (chlorinated benzenes, dichlorodiphenyldichloroethylene - DDE and dichlorodiphenyldichloroethane - DDD) in soils. We optimized the extraction methods for maximum recovery and pre-concentration.

Plasmepsin inhibitory activity and structure-guided optimization of a potent hydroxyethylamine-based antimalarial hit.

Antimalarial hit 1 SR (TCMDC-134674) identified in a GlaxoSmithKline cell based screening campaign was evaluated for inhibitory activity against the digestive vacuole plasmepsins (Plm I, II, and IV). It was found to be a potent Plm IV inhibitor with no selectivity over Cathepsin D. A cocrystal structure of 1 SR bound to Plm II was solved, providing structural insight for the design of more potent and selective analogues.